Gold medals, athletic glory and national pride are all up for grabs at the 29th Summer Olympics in Beijing. But to Veerabhadran Ramanathan, an atmospheric scientist at the Scripps Institution of Oceanography at the University of California at San Diego, the sporting events are just a sideshow to the real excitement: air-pollution studies.

To pre-empt complaints about Beijing's typically horrendous air pollution  the Chinese capital ranks among the world's most polluted urban areas  city officials embarked on a massive cleanup operation in the months and weeks leading up to the Games. Hundreds of dirty factories and power plants were closed down before the Olympics began, and authorities forced at least 2 million cars off the road. Chinese officials are interested in a cleaner Games, since high levels of pollution could be particularly damaging for endurance athletes like marathoners. But to researchers like Ramanathan, these are the Olympics of atmospheric science  scientists can see firsthand the regional effects of the most furious antipollution effort of all time. "The Chinese are performing a grandiose natural experiment," he says. "They've made Beijing a huge lab, and a bunch of us on the sideline are excited over what's unfolding."

So far, it might seem as if the Chinese plan has worked. The air has been remarkably clear in Beijing these days, despite the heavy pollution and the sapping heat and humidity during the opening ceremony and the first couple days of the Games. The first day of the track-and-field events, Aug. 15  when athletes would have been most affected by air pollution  featured a brochure-worthy blue sky. "The recent days have had very good air conditions indeed," said International Olympic Committee medical commission chairman Arne Ljungqvist. Aside from a cycling road race on Aug. 9, which saw more than one-third of the competitors drop out because of the heat, humidity and pollution, few athletes have complained about the air.

But scientists who have long studied Beijing's weather patterns say the blue skies have less to do with the city's $17 billion antipollution programs than with simple meteorology. Kenneth Rahn, a professor emeritus of oceanography at the University of Rhode Island, points out that much of the pollution we see in Beijing is actually brought in on winds, originating in a belt of heavy, dirty industry to the south  plants and factories that have not been turned off during the Games. He estimates that during the city's dirtiest days, about 75% of the pollution would be coming from outside the capital, meaning that, at best, the measures taken by Beijing officials might impact 25% of the pollution overall. "It's really hard to reduce that further," says Rahn. "It's not that the antipollution measures did nothing, but [their effect] is a lot smaller than city fathers would like to admit  possibly so small we can't detect the difference."

Minute differences may be what distinguish gold medalists from mere contenders at the Olympics, but it doesn't quite work the same way with air quality. So Ramanathan, one of the foremost atmospheric scientists in the world, is using Beijing to better understand pollution on a massive scale. Ramanathan and his team are launching a series of unmanned aerial vehicles (UAVs) from South Korea, which will measure the plumes of pollution that rise from the Beijing area and are carried westward. Another UAV will operate in California to determine how much of China's pollution  and which pollutants  make it across the Pacific. "The pollution plumes can be as high as 2 km to 3 km, which has a huge impact," says Ramanathan. "Up at that height, they can travel across the Pacific in three to four days."

In addition to measuring individual pollutants within the plume, Ramanathan's UAVs will use onboard photonic instruments to measure the contributions of various aerosols to atmospheric warming. Here's the surprising thing about the noxious smog that hangs over much of China: it may poison the air, but it also actually offsets global warming. The particles of air pollution form atmospheric clouds, visible by satellite, that reflect sunlight back into space. It's not clear exactly how much the aerosols cool the planet  that's what Ramanathan is trying to figure out  but he believes that without such pollution, Earth might be considerably warmer today.

That means that as developing nations like China clean up their conventional air pollution  as the world is seeing now in Beijing  it could paradoxically release one of the last restraints on global warming. "How large and how rapid global warming is going to be over the next few decades may depend on how fast we unmask the pollution," says Ramanathan. "That's the uncertainty we're trying to narrow down." It's a scary thought: in making our air cleaner, we could be making the planet warmer.

In polluted Beijing, however, such cleanups can and should continue, to make the air clearer not just for Olympians but also for the 17 million people who live there year-round. And if the weather patterns change and the air darkens with smog again before the end of the Olympics, Beijing officials shouldn't bear too much of the blame. Though the spectacle of the Games can make it hard to forget, China is still a developing country, with a developing country's problems  pollution included. "They're trying to squeeze in over the last few weeks a job that should take 30 to 40 years," says Rahn. "No one should be surprised if it doesn't work."